A Graphene Encapsulated Growth Method to form Ultra-thin Magnesium Diboride (MgB₂)

There is interest in coupling 3D topological insulators (TI) with s-wave superconductors (SC) for realizing topological superconductivity (TSC) for quantum computing applications. MgB₂ is an intriguing superconductor for this application as it has T_c = 39K and a hexagonal crystal structure, compatible with common Bi-based TIs. However, MgB₂ oxidizes in air making it difficult to form high quality TI/SC interfaces. Here, we propose a novel approach to synthesize ultra-thin MgB₂ via intercalation between epitaxial graphene (EG) and SiC. EG is used to protect the MgB₂ surface while enabling epitaxial growth of the TI on top. Initial studies investigated Mg intercalation between EG and SiC using a tube furnace. X-ray photoelectron spectroscopy (XPS) and cross section transmission electron microscopy-energy dispersive spectroscopy (TEM-EDS) confirmed Mg intercalation between EG and SiC. Current studies are being performed to optimize process conditions to intercalate Mg. The results of planned investigations to convert Mg to MgB₂ via annealing in B₂H₆ will also be discussed.